refactor(mac): give Window a close operation

Adds Window::close (Backend::close): the same press of the close button
that AdhocWindow::close does on a bare element, applied to the Window's
element. Nothing calls it yet; MacosBackend switches to it in the next
step. No behaviour change: the daemon's own close command still goes through
AdhocWindow on the foreground element, because it has no Window there.

Verified: macOS fake-CC type-check (tools/fast-check) PASS. Not verified:
cannot run or unit-test on Linux.

komorebi-for-mac/komorebi/src/window.rs

@@ -814,6 +814,11 @@ impl Window {
         AccessibilityApi::set_attribute_cf_value(&self.element, kAXMinimizedAttribute, value)
     }
 
+    /// Closes the window by pressing its close button (`Backend::close`); `Ok` when it has none.
+    pub fn close(&self) -> Result<(), AccessibilityError> {
+        AdhocWindow::close(&self.element.0)
+    }
+
     #[tracing::instrument(skip_all)]
     pub fn restore(&mut self) -> Result<(), AccessibilityError> {
         // waiting for what is on its way to the window is not something to do with a lock held